Distributed fibre optic sensing

摘要

Techniques for determining lateral offset of the source of an acoustic disturbance in a distributed acoustic fiber optic sensor are described. The sensor comprises an optical source (112) for interrogating an optical fiber (104) and a detector (116) and processor (108) arranged to detect any backscattered radiation and determine a measurement signal for a plurality of discrete longitudinal sensing portions of the optical fiber. The processor is also arranged to analyse the measurement signals to identify signals corresponding to the same acoustic wave arriving at different parts of the fiber and determine from the time of arrival of said acoustic wave the direction and/or distance of the origin of said acoustic wave from the optical fiber. The geometry of the fiber may be arranged to ensure that any positional ambiguity can be resolved and the use of multiple fibers (501, 502) is disclosed.

主权项

1. A distributed acoustic sensor comprising:
a first length of optical fibre, a source of electromagnetic radiation, a detector apparatus and a processor; a second length of optical fibre running alongside the first length of optical fibre but separated therefrom in a first direction; wherein the source of electromagnetic radiation is configured to launch electromagnetic radiation into said first length optical fibre and said second length of optical fibre; the detector apparatus is for detecting electromagnetic radiation back-scattered from said first length of optical fibre and said second length of optical fibre; and the processor is configured to:
process data corresponding to the detected back-scattered radiation to determine a measurement signal for each a plurality of discrete longitudinal sensing portions of each the first length of optical fibre and the second length of optical fibre;analyse the measurement signal from said longitudinal sensing portions to identify signals corresponding to an acoustic wave arriving at one or more longitudinal sensing portions of the first length of optical fibre and at one or more longitudinal sensing portions of the second length of optical fibre; anddetermine from the time of arrival of said acoustic wave at said longitudinal sensing portions the direction and/or distance of the origin of said acoustic wave from the optical fibre.